1. Field of the Invention
This invention relates to a respiratory mask having an inner mask for covering mouth and nose, wherein the inner mask has at least one inhalation valve, an exhalation valve and a voice aperture intended to be placed opposite the mouth and in which there is located in the inner mask at least one microphone connectable to a transceiver apparatus or an intercom. The invention relates further to a microphone mount for use in such respiratory mask.
2. Description of the Prior Art
A respiratory mask having an inner mask which covers mouth and nose is known from DE 26 43 853 B2. Such respiratory masks connect the mask wearer to a breath protection equipment, as for example a filter insert or a recirculating device. Respiratory masks, in which the inhaled air is first ducted via a first inhalation valve in the form of a check valve into an outer mask cavity located outside the inner mask and then is ducted to the breathing passages via at least one additional inhalation valve in the form of a check valve through an inner mask cavity located inside the inner mask, are referred to as scavenging masks. The exhaled air is ducted directly from the inner mask to the outside via an exhalation valve in the form of a check valve. In such a scavenging mask there therefore exist separate paths for conducting inhaled and the exhaled air. The first inhalation valve, which leads into the outer mask cavity, is positioned above a voice aperture in the inner mask cavity, which becomes positioned opposite the mouth. The voice aperture is covered by a voice diaphragm on that side which faces the inner mask cavity. When the mask wearer speaks, the voice diaphragm is set into oscillation, whereby the speech is transferred to the outside. With the respiratory mask in place, drawn-in inhaled air flows through the first inhalation valve above the voice aperture into the outer mask cavity and from there is led, as determined by the configuration of the inner mask, past a mask window through at least the second inhalation valve into the inner mask. There it flows toward the air passages of the mask wearer. The exhaling to the outside takes place through the exhalation valve provided in the chin region of the mask. This kind of breathing air ducting is accompanied by high noise production. This noise production has hardly any harmful effect on the operation of the voice diaphragm. However, currently it is desired to equip such respiratory masks with a microphone so that the mask wearer while on duty can also communicate over greater distances with other persons, a control post or the like. In that case, the breathing noise which is produced is extremely harmful to the voice reproduction.
From DE 33 42 063 A 1 there is known a respiratory mask of the kind defined in the introducing part of the specification, in which a microphone is positioned in the inner mask cavity and is connected to a transceiver apparatus or the like through a microphone connecting conductor which is led to the outside in sealed manner through one of the fittings located in the body of the respiratory mask, such as the support for the exhalation valve. In so doing, the microphone is attached to the interior of the inner mask right next to the exhalation valve. By this arrangement of the microphone, there is supposed to be achieved not only an excellent quality of reproduction but sealing difficulties are also supposed to be avoided. But nowadays, the reproduction quality of such an arrangement of the microphone is no longer considered to be satisfactory. The high noise production caused by the air flowing through the in- and exhalation valves has too disturbing an effect on the reproduction. From DE 33 42 063 A 1 it can also not be determined with what type of mount the microphone is attached to the inside of the inner mask.
From U.S. Pat. No. 4,737,740 there is known a gas mask with microphone in which the microphone is located in the inside in a manner similar to that of the respiratory mask according to DE 33 42 063 A 1, but in addition there is also provided a voice diaphragm like that of the respiratory mask according to DE 26 43 853 B2. In addition to the high noise production, which is caused by the air flowing through the in- and exhalation valves, noises from outside are transmitted into the inside of the gas mask through the voice diaphragm, whereby the tonal quality of the microphone is still further degraded.
Finally, from U.S. Pat. No. 5,307,793 there is known a respiratory mask with microphone in which the effect on the microphone of the air noise produced during in- and exhaling is precluded with the aid of mechanical devices which disconnect or cover the microphone during the breathing process. This is a costly method of improving the tonal quality of the microphone. Moreover this method requires a specially constructed respiratory mask so that other respiratory masks, which do not have the same construction, can not be retrofitted according to this method.